AERs from the left and right temperoparietal and occipital cortex were recorded using visual stimuli presented to the left and right hemiretinal fields. Subjects included normal controls and patients with acute schizophrenia, affective illness and right and left temporal lobectomies for epilepsy. Subjects were asked to perform two tasks; counting flashes and doing mental arithmetic. Differences in AER caused by attention were noticed especially in the left temperoparietal cortex route. Schizophrenic and lobectomy groups showed diminished asymmetry and attentional effects whereas bipolar affective disorders showed generally enhanced attentional effects. Data analysis is currently underway on this project.